Reverse current relay



Aug. 28, 1951 R. L. BROWN REvERsE CURRENT RELAY Filed March 11, 1947 INVENTOR RUBEHT L. BHUll/N ATTORNEY Patented Aug. 28, 1951 nEvERsE CURRENT RELAY Robert Lowell Brown, Teaneck, N. J assignor to Bendix Aviation Corporation, Teterboro, N. J

acorporation of Delaware Application March 11, 1947, Serial No. 733,937

The present invention relates to means for eliminating arcing at the contacts'of a trigger relay of the difierential reverse current relay type in generator systems of aircraft.

An object of the invention is to provide in a generator system a relay including voltage and current coils and in addition an auxiliary antiarcing coil whereby additional ampere turns are momentarily added upon the closing of the relay contacts to assist the eifect of the voltage coil and accentuate the engagement of the relay contacts to prevent an arcing or trembling action.

Another object of the invention and a novel feature thereof is to'provide a main line switch relay controlled by the reverse current relay and eiiective upon closing for opening the circuit of the auxiliary anti-arcing coil.

Another object of the invention is to so arrange the main line switch relay that the closing thereof will simultaneously open the circuit for the auxiliary anti-arcing coil and a parallel circuit for energizing a portion of the electromagnetic coil of the main line switch relay.

These and other objects and. features of the invention are pointed out in the. following description in terms of the embodiment thereof which is shown in the accompanying drawing.

It is to be understood, however, that the drawing is for the purpose of illustration only, and is not designed as a definition of the. limits of the invention, reference beinghadto the appended claims for this purpose.

The drawing as a schematic diagram illustrating the present invention in which the several relays are shownin a deenergized position.

Referring to the drawing there is shown a generator I having output lines.2 and 3. Line 3 is grounded while line 2 maybe connected through a main relay switch 4 to a line 5 leading to the positive terminal of a battery 6. The opposite terminal of the battery 6 is ground connected through a conductor 1 to the conductor. 3 of the generator I. l

The main relay switch 4 is biasedby a spring 8 into an open position. The relay switch 4 has electromagnetic windings 9 and II) which are connected in series and are arranged to actuate the relay switch 4 into a closed position upon energization.

One end of the series connected winding I is grounded by a conductor ll whilejthe opposite end of the winding 9 is connected by a conductor I2 to a reverse current relay switch i3.

' The reverse current relay switchflS cooperates with a contact I4 and is biased by aspring T in 4 Claims. (01. 175-294) a contact open position. The contact I4 is connected by a conductor I! through a manually operable switch 18 to the output line 2 of the generator I.

Connected to the conductor I7 is a voltage coil I9 grounded at 20 and arranged so as to affect the reverse current relay switch l3.

Also connected to the conductor I! is another voltage coil 2| grounded at 22 and controlling a relay switch 23. The relay switch 23 cooperates with a contact 24 and is biased to a contact open position by a spring 25. The contact 24 is connected by a conductor 26 to the battery line 5,

while the switch 23 is connected by conductor 21-- through ballast lights 28 to one end of a differential coil 29 which also effects the-reverse current relay switch [3. The opposite end of the differential coil 29 is connected by a conductor 39 to the generator output line 2.

It will be seen then that upon the closing of the switch [8 and energization of the winding ill the differential coil 29 will be connected between the generator output line 2 and the battery input line 5 and in series relation between the generator and battery. Moreover, the closing of switch l8 will also connect the voltage coil l9 across the output of the generator I. The differential coil 29 is arranged so as to effect with the voltage coil IS the closing of the relay switch l3 upon the generator output voltage exceeding the battery voltage by a predetermined value of, for example, one volt. If the battery voltage be greater or there be a current flow from the battery 6 to the generator I, the electromagnetic force of the coil 29 .Will oppose that of the voltage coil l3 so that switch [3 will be retained in an open position by spring l5.

With the switch i3 closed, the main line switch 4 is biased to a closed position by action of the electromagnetic windings a and it as will be explained.

There is further connected in series in the generator output line 2 a reverse current winding 3| which becomes effective upon the closing of the line switch 4.

The voltage coil I9 is arranged so as to hold relay switch i3 closed for no reverse current from the battery 6, but in the event of a flow of reverse current from the battery 6, the reverse current winding 3| will oppose the electromagnetic force of the voltage coil I9 that switch [3 under force of the spring [5 will be biased to an open position.

Also affecting the reverse current relay switch l3;and forming a novel feature of the present in vention is an additional anti-arcing coil-32-which is connected through a conductor 33 to the line I2 leading from switch I3. The opposite end of the anti-arcing coil 32 is connected by a conductor 34 to a switch 35 cooperating with a contact 36 and biased to a contact closing position by a spring 31. The contact 36 is connected by a conductor 38 to the series connection between the coil 9 and coil II] of the main line relay. A rod 39 connects switch 4 to the switch 35 so that upon actuation of the switch 4 to a closed position by the action of the electromagnetic coils 9 and II], the switch 35 is simultaneously actuated to an open contact position. It will be seen then that upon the closing of relay switch I3 the coil 9 will be connected to the generator output line 2 in parallel to the anti-arcing coil 32, and the two coils 9 and 32 will be connected through coil I to the ground and the opposite terminal of the generator I. between the contact I4 and switch I3 will immediately give an added impulse to the switch I3 through the action of the anti-arcing coil 32.

Operation A better understanding of the novel improvement may be received from a description of the sequence of operations of the relays for the conditions of a live line, with the incoming generator slowly increasing its output voltage and the switch I8 closed. 7

When the incoming generator voltage reaches a value of, for example, approximately 90-100 volts, the spring opposed relay 23 closes, thus closing the circuit of the differential winding 29 of the relay I3. Relay I3, however, does not close since the current through the differential winding 29 will be in such a direction as to tend to hold relay I3 open, i, e., the current through the differential winding 29 then aids the spring I which tends to hold relay I3 open. In the conventional systems, when the incomin generator rises above the line by, for example, approximately one half volt and hovers there, but is subject to additional plus or minus one volt variation due to the unsteady running of the generator I (as would be commonly produced by the power pulses in a driving internal combustion engine), had arcing may be produced at the contact correspondin to contact I4 of relay I3. Thus such contact will alternately be partially closed and open respectively, in cases where the present invention is not employed, by the plus and minus one half volt difierential acting through the difierential winding 29. This would then occasionally cause such contacts I3 and I4 to draw out a bad arc before they close sufficiently to cause full closure of the main line switch 4. If, however, as in th present invention a few turns (winding 32) are wound on the magnetic core affecting relay I3 and the winding is connected in series with the contact relay I3 and the pull-in winding III of the main line switch 4, then any arcing current that may start at the contacts of relay I3 will immediately give an added closin impulse to the relay [3 through the action of the winding 32 thus preventing the drawing out of an arc at the contacts I3I4.

In the present invention, when relay I3 closes, the current flow through the windin 9 (mainly) and I0 (partially) of the main line switch 4 causes the switch 4 to close. When the main line switch 4 closes, the rod 39 causes switch 35 to simultaneously open and hence the circuit through windings 32 of relay I3 and II] of the main line switch 4. Also the closing of the main line switch 4 shorts out the differential winding 29 in relay I3.- This Any arcing current that may start then leaves relay I3 with only the electromagnetic force furnished by the holding winding I9 which is suflicient to hold relay I3 closed.

When the generator voltage decreases below the line voltage, the resultant reverse current flow in the series main line winding 3| will cause relay I3 to open and thus cause the main line switch 4 to open.

Although only on embodiment of the invention has been illustrated and described, various changes in the form and relative arrangements of the parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is, therefore, to be had to the appended claims for a definition of the limits of the invention.

., What is claimedis:

l. The combination of cooperating electric contacts,ispring means for urging the contacts apart, electromagnetic means for urging the contacts together, means including an auxiliary winding in series with said contacts for increasing the magnetic force urging the contacts together after initial closure thereof and upon said contacts tending to open thereafter, a main line switch, electromagnetic means for closing said switch and controlled by said contacts, and said last mentioned electromagnetic means including independent switch means normally biased in a closed position for rendering said magnetic force increasing means ineffective during the full closure of said contacts and simultaneously with the closing of said mainline switch.

2. In a generator system of the class including a reverse current relay switch and a main line relay switch controlled thereby; the improvementcomprising an auxiliary winding in series circuit relation with said reverse current relay switch and responsive to arcing current therein for effecting said reverse current relay switch, a third switch element normally biased to a closed position for controlling said auxiliary winding, said reverse current relay switch effecting an energizing circuit .for said auxiliary winding upon closing so as to prevent vibration of said reverse current relay switch, and means operably connecting said third switch element to said main line relay switch for opening the energizing circuit of said auxiliary winding upon the closing of said main line switch and during th full closure of said reverse current relay switch.

3. In a generator system. of the class including a reverse currentrelay having a voltage coil, a differential coil, and a current coil, said coils arranged to electromagn-etically operate a switch element, a main relay having an electromagnetic winding and a main line switch element controlled thereby, said reverse current relay switch element controlling the energization of said main line relay Winding; the improvement comprising an anti-arcing coilin series with said reverse current switch element and responsive to arcing current therein so as to increase the magnetic force acting thereon upon the closing of said last mentioned switch element and to prevent vibration thereof, athird switch element normally biased to a closedposition, mechanical means operably connecting said main line switch element to said third switch element, said third switch element controlling the energization of said anti-arcing coil and affected by said mechanical means to deenergize said anti-arcing coil upon the closing ofv said main line switch and during the full closure of said reverse current switch elementy.

4. In a generator system of the class including a reverse current relay switch and a main line relay switch controlled thereby; the improvement comprising an auxiliary winding connected in series with said reverse current relay switch, a third switch element normally biased in a closed position for controlling said auxiliary winding, said reverse current relay switch effecting an energizing circuit for said auxiliary winding upon closing, said energizing circuit being responsive to arcing current in said reverse current relay switch to aid the closing thereof, and means operably connecting said third switch element to said main line relay switch for opening the energizing circuit of said auxiliary winding upon the closing of said main line switch.

ROBERT LOWELL BROWN.

6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 727,713 Thomson May 12, 1903 1,763,202 Van Sickle June 10, 1930 2,211,701 McGrath Aug. 13, 1940 10 2,254,039 'Kovalsky Aug. 26, 1941 2,359,175 Walley Sept. 26, 1944 FOREIGN PATENTS Number Country Date 60,861 Switzerland Apr. 20, 1912 197,106 Great Britain May 10, 1923 

